Tag Archives: midi


LPC1114 controlled Midi Synthesizer

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Matt Sarnoff built this digital monophonic synthesizer using the NXP LPC1114FN28 ARM Cortex-M0 microcontroller and MCP4921 SPI DAC. It is a midi synthesizer with following features:

  • 4 oscillators; sawtooth or pulse with adjustable duty cycle with coarse and fine tuning
  • 2-pole (“Chamberlin”) state-variable filter with lowpass, highpass, and bandpass modes
  • Attack-release envelopes for amplitude and modulation
  • Low-frequency oscillator with four shapes (triangle, ramp, square, random)
  • LFO and/or modulation envelope can affect filter cutoff frequency, pitch, and pulse width
  • Keyboard tracking for filter cutoff frequency
  • Glide with 3 different rate presets
  • MIDI input; monophonic with last-note priority
  • 250kHz, 12-bit output
  • Powered by 3 AA batteries
ARM-powered midi synthesizer

ARM-powered midi synthesizer

DIY audio/video transport control surface

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Audio/video transport controllers are used in recording studios and live performance setups for quick hands-on control on demanding editing or mixing tasks. These devices are an expensive piece of hardware (costs from a few hundreds to thousands of USD). Victor Frost’s OpenTransport project would allow hobbyists to build an external transport control surface at very low price. It is an open-source, open hardware transport controller that sends out MIDI commands and therefore, works with most of the Digital Audio Workstation and Digital Video Workstation softwares. It is Arduino-powered and provides controls for play, stop, fast forward, rewind, record, loop, and mackie keys Function 1 and Function 2, which are configurable.

OpenTransport: An open-source control surface

OpenTransport: An open-source control surface